Method for disinfecting medical instruments and apparatus



Dec. 2, 1969 KARL-GUSTAF E. ROSDAHL ET 3,481,689

METHOD FOR DISINFECTING' MEDICAL INSTRUMENTS AND APPARATUS Filed Nov. 10, 1966 Fig.1

INVENTOR KarL- Guslzm Engelbrekt Rosdqhl CarL- G-urmqrDan/eL Engst riim BY Paul. Herzo JPW JWN v ATTORNEYS United States Patent US. Cl. 21-58 1 Claim ABSTRACT OF THE DISCLOSURE A method for disinfecting and sterilizing delicate surgical instruments and medical apparatus includes forming an aerosol of an aqueous ethanol solution in a carrier gas by ultrasonic vibrations and contacting the instruments or apparatus with the aerosol. After disinfection the aerosol remaining on the instruments may be removed by scavenging with the carrier gas alone.

The present invention relates to a device for disinfecting apparatus and instruments, preferably medical ones.

When cleaning apparatus and instruments for the purpose of sterilization there often arises the problem of cleaning interior parts in for instance, complicated respiration apparatus for medical use, which are difficult to get access to and include delicate elements. In a procedure of this kind there are two measures, which are necessary, namely supplying disinfecting agent in such a way so as to bring it into contact with all interior corners and cavities in the apparatus to be disinfected, and removing the disinfecting agent and also the solvent therefore, so that the apparatus becomes dry and ready for reuse. In a known method of disinfecting apparatus so-called through-rinsing or flushing with disinfecting agent in liquid form is used, which method, however, cannot be applied when dealing with elements which are difficult to dismount or are fragile, for instance valve systems, gas meters etc. in breathing apparatus. Said method has the drawback of using great amounts of disinfecting agent and also the drawback that it is difiicult afterwards completely to remove the disinfecting agent, so that the apparatus becomes dry and ready for use. Another method of disinfecting is gas-disinfecting, with ethylene oxide, which agent, however, is strongly toxic and requires special precautions, and yet another, the method of sterilization by heating, for instance in an autoclave, which, however, is inconceivable' for apparatus having fragile members not resisting an increased temperature.

Therefore, the present invention has for its object to remove the drawbacks indicated above and provide a method for an efficient and yet mild sterilization of apparatus or instruments, preferably medical ones. In the method according to the invention the disinfection is carried out by means of a disinfecting agent carried by a gas, and the method comprises passing a carrier gas to an ultrasonic atomizer, in which the disinfecting agent is atomized and transferred into the carrier gas to form an aerosol, which is then brought into contact with the apparatus or instruments, and then possibly drying the apparatus or instruments by interrupting the atomization and passing carrier gas alone into contact therewith. The disinfecting agent can be ethanol, preferably a 70% aqueous solution thereof, or disinfecting agents dissolved in ethanol.

By using as a disinfecting agent an aerosol formed by 3,481,689 Patented Dec. 2, 1969 atomizing a liquid disinfectant into a carrier gas by means of an ultrasonic atomizer surprisingly good results are obtained. This is obviously due to the fact the an aerosol generated by using ultrasonic waves has a great stability as compared to aerosols formed by conventional means, for instance mechanical disintegrators, such as rotating impellers splitting up the liquid to be atomized into droplets. The superior stability of ultrasonic generated aerosols is due to the fact, firstly, that the diameter of the liquid droplets in the aerosol is very small and, secondly, that said diameter varies within a relatively narrow range, particularly as compared to aerosols generated in a conventional manner. For instance, water atomized by means of an ultrasonic atomizer energized at a frequency of 3 megacycles/sec. gives droplets of an average diameter of about 1.3 micron. The diameter of the particles generated is dependent on the viscosity of the liquid to be atomized and decreases with decreasing viscosity. Thus, when using a aqueous solution of ethanol the particles generated are even smaller, having a diameter of about 0.6 micron, in view of the lower viscosity of ethanol as compared to water.

The fact that the aerosol produced has a surprising stability and that the particle size is very small has for an effect, that the disinfection obtained is very effective in view of the great active surface of the aerosol particles and that there is little precipitation of liquid in the apparatus or instruments to be disinfected. In view of this it is very easy after the disinfection to remove the residual liquid so as to render the disinfected object ready for use.

Obviously, the present invention can be used when disinfecting rooms, apartments and the like, and also in this case the stability of the aerosol is of a great importance as it enables avoiding deleterious effects on expensive furniture, paintings etc. contained in the infected accommodation.

The invention also provides a device for carrying out the method of the invention, and the device comprises an ultrasonic atomizer having an atomizing chamber and an inlet thereto and an outlet therefrom for supplying a carrier gas and discharging aerosol formed in the ultra-sonic atomizer, respectively, driving means connected to the supersonic atomizer, preferably the inlet thereof, for propelling the carrier gas and means for passing the aerosol formed into contact with the apparatus or instruments. The driving means can be a pressure tube connected to the inlet containing carrier gas or a fan connected to the inlet.

An embodiment of the device of the invention particularly useful for sterilizing small instrument Such as scalpels syringes and the like, comprises an openable container having an inlet and an outlet, the inlet of which is connected to the outlet of the ultrasonic atomizer and being adapted to contain the instruments, the container preferably being provided with an interior horizontal grid for supporting the instruments during the disinfection.

In all embodiments of the device of the invention a variable restriction, such as a control valve or strangler, can be arranged in the flow path of the carrier gas of the aerosol for controlling the flow resistance and thus the flow rate of the aerosol.

The invention will now be gtnore closely described by means of examples with reference to the appended draw- FIG. 1 shows diagrammatically an embodiment of the device of the invention having a pressure tube as driving means.

FIG. 2 shows diagrammatically another embodiment of the device of the invention having a fan as driving means.

FIG. 3 shows in section and more in detail an ultrasonic atomizer for atomizing disinfecting agent.

FIGS. 1 and 2 show diagrammatically two different arrangements of the invention for disinfecting medical instruments.

The device of FIG. 1 consists of an ultra-sonic atomizer 1 and a pressure tube 3 connected thereto. The ultra-sonic atomizer 1 is adapted for the atomization of a disinfecting agent, which is supplied from above from a diagrammatically indicated funnel 5 having a shut-off cock 7. The ultra-sonic atomizer 1 which is described more closely below has an inlet 9 connected to the pressure tube 3 and an outlet 11. The pressure tube 3 is provided with a restriction or control valve 13 such as a needle valve for controlling or varying the gas flow.

The outlet 11 of the ultra-sonic atomizer 1 is connected to a diagrammatically indicated rnedical apparatus 17 to be disinfected through a conduit 15. For instance, the apparatus 17 can be a heart-lung machine having a complicated tube system the interior of which is difiicult to get access to.

Briefly, the function of the device of FIG. 1 is the following. A suitable gas fiow from the pressure tube 3 to the ultra-sonic atomizer 1 is obtained by adjusting valve 13, and by adjusting the cock 7 of the funnel 5 a suitable drop rate for the disinfecting agent is obtained. When passing through the ultra-sonic atomizer 1 the gas from the pressure tube 3 is supplied with atomized disinfection agent to the formation of an aerosol, which leaves through the outlet 11 and is transferred to the apparatus 17 through the conduit 15. The connection to the apparatus 17 can be done at any suitable location of the conduit system of the apparatus, and the aerosol can be brought to flow in a closed circuit inside, or through the apparatus. After a while of passing aerosol containing disinfecting agent through the apparatus 17 said agent having contacted all of the inner parts of the apparatus, the supply of disinfecting agent to the ultra-sonic atomizer 1 is interrupted by closing the cock 7, the apparatus 17 then being dried by continued flushing of carrier gas alone. A manifold increase of the gas flow can be obtained by de' creasing the flow resistance of the valve 13. In this way an eflicient disinfection of the apparatus 17 can be obtained with a minimum use of disinfecting agent, Moreover in the manner indicated above the interior of the apparatus can be dried fast and efiiciently so as to be ready for use immediately.

In the device of FIG. 2a conventional fan 19 is used as a driving means feeding the ultra-sonic atomizer 1 with carrier gas. A restriction or control valve 20, such as a throttle valve, for controlling or varying the flow of carrier gas is provided in the conduit between the fan 19 and the ultra-sonic atomizer 1. The conduit extending from the outlet 11 of the ultra-sonic atomizer 1 is connected to a container 21, which at its upper end is provided with a hinged lid 23. Inside the container 21 there is provided a horizontal grid 25. An electric heating element 27 is provided in connection to the conduit 15 for a purpose to be described below.

The device of FIG. 2 is primarily adapted for the disinfection of small medical instruments 29, such as scalpels, tongs, syringes or the like, which are positioned on the grid in the container 21, the lid 23 then being closed. The disinfection is then carried out in a similar way as described in connection to FIG. 1. If desired a closed system can be used by recirculating the aerosol discharged from the container 21 through a return conduit 28 (diagrammatically indicated with a dashed line) to the fan 19.

The drying of the sterilized instruments 29 can be facilitated by heating the carrier gas passed through the container 21 by means of the fan 19 by actuating the element 27 after having interrupted the su ply of disinfecting agent.

An embodiment of an ultra-sonic atomizer useful for the atomization is now to be more closely described in connection with FIG. 3 showing a vertical section of the atomizer.

The ultra-sonic atomizer consists of a container having side walls 62, a bottom 63 and a removable lid 64, which is connected to the side walls 62 by means of a gastight gasket 65. Said members form an atomizing chamber containing an atomizing space 68. The chamber has a gas inlet 69 for the supply of carrier gas and a gas outlet 70 for the aerosol discharged. In the bottom of the atomizer an ultra-sonic vibrator 72 is arranged having a plane vibrator plate 73, which is supplied with high frequency current of f.i. 3 megacycles/ sec. through the coaxial cable 74. At the bottom of the atomizer there is also a drain pipe 76 having a cock 77. The disinfecting agent to be atomized is supplied from a bottle 80 suspended from a bracket 81. The bottle may be an ordinary hospital drop flask intended for use in blood transfusions. The bottle 80 is suspended upside down and is sealed with a plug 82, through which there is passed a liquid discharge pipe 83 and an air admitting pipe 84, reaching up adjacent to the bottom of the bottle. As disinfecting agent is consumed, air enters through the pipe 84. The liquid passes, when jam-nut 87 is open, from the bottle 80 through the flexible tube to the conduit 88, which is passed through the lid 64 through a sealing plug 89 and opens some distance above the vibrating plate 73. The conduit can be extended to a position close to said vibrating plate, but in view of the difficulty of accurately determining the distance between the opening of the conduit and the plate 73, preferably, a funnel 91 is positioned between the opening of the conduit 88 and the plate 73. The opening 92 of the funnel can be set with sufiicient precision at the desired distance above plate 73, and said distance should be at least 0.1 mm. and is preferably 1-2 mm. The conduit 88 is assumed to be a capillary tube or having a capillary portion at its opening 90, the capillary diameter being, for instance, 0.1-0.2 mm.

By hanging the bottle 80 at an appropriate height above the ultra-sonic atomizer the desired flow of liquid can be obtained, which may be 10-20 drops per minute. Although the amount of liquid supplied should be estimated to be fully atomized it may happen that liquid splashes from the vibrating plate 73. In order to collect such splashes and refeed same to plate 73, baffle means are preferably arranged above the vibrating plate. In the example illustrated the bafiies are arranged in the form of an inverse truncated cone 95 having openings 96 between the bafiles 97.

In order to facilitate the transfer of liquid from the funnel or from the opening of the conduit 88, in case no funnel is used, on to the plate 73, a leader thread 98 may be arranged between the opening of the funnel or the conduit, respectively, in or in the neighborhood of the vibrating plate 73.

By means of the ultra-sonic atomizer shown in FIG. 3 the amount of disinfecting agent supplied is easily adjusted relative to the flow of carrier gas to obtain maximum disinfecting efiiciency. By closing the jam nut 87 the supply of disinfecting agent to the ultra-sonic vibrator is easily interrupted and it is then possible, possibly with a manifold increase of the carrier gas flow, rapidly to dry the apparatus or the instruments having been disinfected. This drying efficiency can be further increased by mounting a heating element in the flow path of the carrier gas such as the electric element 27 of FIG. 2.

As a disinfecting agent all known liquid agents can be used and a preferred agent is ethanol, which is suitably used in the form of a 70% aqueous solution. Solid disinfectants dissolved in ethanol, water or other suitable solvent can also be used. Air, nitrogen gas or other gases, which do not effect the disinfecting agent used, can be used as a carrier gas.

The invention is of course not limited to the embodiments shown herein concerning atomizer, driving means,

the position thereof etc. It is thus also possible to place the driving means between the ultra-sonic atomizer and the apparatus to be disinfected. An ejector pump, for instance a conventional water ejector, can be used as a driving means and is connected to a point downstream of the object to be disinfected, for instance at the outlet of container 21 (FIG. 1).

What is claimed is:

1. A method of disinfecting and sterilizing medical instruments and apparatus comprising atomizing by ultrasonic vibrations a disinfecting agent consisting essentially of an aqueous ethanol solution containing about 70% ethanol by weight, in the presence of an inert carrier gas stream to form an aerosol, contacting the instruments to be disinfected with the aerosol and thereafter continuing to contact said instruments with the inert carrier gas stream to remove the disinfecting aerosol remaining thereon.

References Cited UNITED STATES PATENTS MORRIS O. WOLK, Primary Examiner B. S. RICHMAN, Assistant Examiner U.S. Cl. X.R. 

